But things usually don't get better over time. Instead of extending the time with the yeast, conditioning either in the bottle or the keg would be the answer.
If the beer tastes bad before it goes in the bottle, it will taste bad when it comes out. It might not be as bad but bad none the less.
I'm not sure how you scorched the grains in the first place unless you are heating the mash tun. The bottom line is that you have learned a valuable lesson and have a plan to ensure that future brews do not have this problem.